Compact Interactive Tabletop with Projection-Vision

ABSTRACT

The subject application relates to a system(s) and/or methodology that facilitate vision-based projection of any image (still or moving) onto any surface. In particular, a front-projected computer vision-based interactive surface system is provided which uses a new commercially available projection technology to obtain a compact, self-contained form factor. The subject configuration addresses installation, calibration, and portability issues that are primary concerns in most vision-based table systems. The subject application also relates to determining whether an object is touching or hovering over an interactive surface based on an analysis of a shadow image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/110,637 filed on May 18, 2011, entitled “Compact Interactive TabletopWith Projection-Vision,” which is a continuation of, and claims priorityto U.S. patent application Ser. No. 12/554,827, now U.S. Pat. No.7,970,211, entitled “Compact Interactive Tabletop WithProjection-Vision,” filed on Sep. 4, 2009, which is a continuation of,and claims priority to U.S. patent application Ser. No. 11/363,750, nowU.S. Pat. No. 7,599,561, entitled “Compact Interactive Tabletop WithProjection-Vision,” filed on Feb. 28, 2006, the entire disclosures allthree of which are incorporated by reference herein in their entireties.

BACKGROUND

The advent of novel sensing and display technology has encouraged thedevelopment of a variety of interactive systems which move the input anddisplay capabilities of computing systems on to everyday surfaces suchas walls and tables. The manner in which this has been done in currentsystems indicates an attempt to address design and integrationobjectives. However, such systems remain deficient in their variety ofsensing capabilities, suitability to easy installation and calibration,and/or usability of the systems among consumers.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of the systems and/or methods discussedherein. This summary is not an extensive overview of the systems and/ormethods discussed herein. It is not intended to identify key/criticalelements or to delineate the scope of such systems and/or methods. Itssole purpose is to present some concepts in a simplified form as aprelude to the more detailed description that is presented later.

The subject application relates to a system(s) and/or methodology thatfacilitate sensing of objects and co-location of projection of any image(still or moving) onto any surface. In particular, a front-projectedcomputer vision-based interactive table system is provided which uses anew commercially available projection technology to obtain a compact,self-contained form factor. The subject configuration addressesinstallation, calibration, and portability issues that are primaryconcerns in most vision-based table systems. More specifically, theprojector and cameras, as well as computing resources such as CPU andstorage, can be built into the same compact device. This combinedprojecting and sensing pod may be readily placed on any flat surface inthe user's environment and requires no calibration of the projection orsensing system. It is this portability, ease of installation, andability to utilize any available surface without calibration that tendsto be more important or even required for mainstream consumeracceptance. For example, imagine a child pulling such a device out ofthe closet and placing it on a table or the floor of their room totransform the nearby surface into an active play, school work, orentertainment space.

The subject system is capable of sensing a variety of objects anddisplaying animated graphics over a large display surface and uses a newcommercially available projection technology to obtain an exceptionallycompact, self-contained form factor. Unlike many other conventionalsystems, this system may be quickly set up to operate on any flatsurface, requires no calibration beyond the factory, and is compactwhile still displaying and sensing over a large surface area such as awall, floor, or elevated surface (e.g., platform, table, or desk). Thesefeatures make it especially attractive in consumer applications, wheredistribution, installation, mounting, and calibration considerationstend to be paramount.

Furthermore, image processing techniques for front-projectedvision-based table systems are also provided. These techniques include ashadow-based touch detection algorithm, a fast and uncomplicated visualbar code scheme tailored to projection-vision table systems, the abilityto continuously track sheets of paper, and an optical flow-basedalgorithm for the manipulation of onscreen objects that does not rely onfragile tracking algorithms.

To the accomplishment of the foregoing and related ends, certainillustrative aspects of the invention are described herein in connectionwith the following description and the annexed drawings. These aspectsare indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed and the subject invention isintended to include all such aspects and their equivalents. Otheradvantages and novel features of the invention may become apparent fromthe following detailed description of the invention when considered inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a projection-vision system that can senseand display objects onto any surface using a unique front projectionassembly to facilitate creating an interactive surface or workspace.

FIG. 2 depicts an exemplary projection-vision system that can beemployed to sense and display objects on any surface.

FIG. 3 is a block diagram that compares conventional projection systemswith the subject projection system.

FIG. 4 demonstrates an input image and a corresponding rectified imagethat is displayed on an interactive surface.

FIG. 5 is a block diagram of a projection-vision system that can sensevisual coded objects touching any interactive surface.

FIG. 6 demonstrates a 3D graphics model which has been projected onto anidentified game piece (left) and a 12 bit code given by the patternaround the edge (right).

FIG. 7 demonstrates a blank sheet overlapping a printed sheet (top view)and the same image rendered on a surface having two different imagesprojected onto each sheet (bottom view).

FIG. 8 is a block diagram of a projection-vision system that candetermine whether objects are hovering or touching the surface viashadow analysis.

FIG. 9 demonstrates an aspect of shadow analysis as it is employed todistinguish between hovering over the interactive surface and touchingthe surface, and in particular an input image and a resulting binarizedimage.

FIG. 10 depicts a close-up view of the binarized image in FIG. 9 to moreclearly distinguish between shadows on or over the interactive surface.

FIG. 11 demonstrates at least two exemplary applications of aprojection-vision system.

FIG. 12 is a flow diagram illustrating an exemplary methodology thatfacilitates determining whether an object is touching or hovering overthe interactive surface.

FIG. 13 is a flow diagram illustrating an exemplary methodology thatfacilitates page tracking and projecting images on such pages.

FIG. 14 illustrates an exemplary environment for implementing variousaspects of the invention.

DETAILED DESCRIPTION

The subject systems and/or methods are now described with reference tothe drawings, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the systems and/or methods. It may beevident, however, that the subject systems and/or methods may bepracticed without these specific details. In other instances, well-knownstructures and devices are shown in block diagram form in order tofacilitate describing them.

As used herein, the terms “component” and “system” are intended to referto a computer-related entity, either hardware, a combination of hardwareand software, software, or software in execution. For example, acomponent may be, but is not limited to being, a process running on aprocessor, a processor, an object, an executable, a thread of execution,a program, and a computer. By way of illustration, both an applicationrunning on a server and the server can be a component. One or morecomponents may reside within a process and/or thread of execution and acomponent may be localized on one computer and/or distributed betweentwo or more computers.

Referring now to FIG. 1, there is a general block diagram of aprojection-vision system 100 that can sense and display objects onto anysurface using a unique front projection assembly to facilitate creatingan interactive surface or workspace. The system 100 includes acamera-projection component 110 that comprises a projector, at least onecamera, and an infrared illuminant which are assembled as a single piecethat is designed to sit on a flat surface such as a table, desk, wall,or floor. FIG. 2 illustrates an exemplary configuration 200 of theprojection vision system 100 and will be described together with FIG. 1.

By configuring the system as a single unit, it can be made compact andmore portable for user convenience. With portable projection systems,one thought that often comes to mind is calibration—or ratherre-calibration which is often required in a conventional projectionsystem after the system is moved. However, in an exemplary configurationof the subject system 100 as represented in FIG. 2, the projectoremployed can be an NEC WT600 DLP projector which can project a 40″diagonal image onto an ordinary horizontal surface. Four game pieces 210and a real piece of paper 220 are detected on the surface in FIG. 2.

The NEC WT600 is an unusual projector in that it uses four asphericmirrors (no lenses) to project a normal 1024×768 rectangular image froma very oblique angle, and at extremely short distance. For a 40″diagonal image, the WT600 requires 2.5″ between its leading face and theprojection surface, while a 100″ diagonal image is obtained at adistance of 26″. These characteristics make it very well suited for thesystem 100, in that it allows for the projector to sit directly on theprojection surface (on a short pedestal), rather than be hung suspendedover the surface.

As in other projection-vision systems, the scene (display space) can beilluminated with an infrared source and all but infrared light can beblocked to the camera with an infrared-pass filter. This effectivelyremoves the projected image from the scene. The projector provides anatural place to mount one or more cameras and an infrared illuminant.By rigidly mounting the cameras and illuminant to the projector, thecalibration of the vision system to the display is the same regardlessof where the unit is situated and may be determined at the factory.

One method to perform sensing and detection of objects on the surface isto use two cameras and simple stereo calculations as has been done intraditional systems, but in the subject system 100, one camera isemployed combined with image techniques that allow touch detection byexamining the shadows of objects, detailed later in FIGS. 8-11. The IRilluminant is positioned off axis from the single camera so that objectsabove the surface generate controlled shadows indicating height. In thisparticular exemplary configuration (in FIG. 2), the system 100 uses anOpto Technology OTLH-0070-IR high power LED package and a Sony ExViewanalog gray-scale CCD NTSC camera. The ExView was chosen for its highsensitivity in the near infrared domain. To minimize the size of theoverall unit, the camera can be mounted near the top of the projector,giving an oblique view of the surface. A very wide angle micro lens (2.9mm focal length) is suitable to capture the entire projected surface. Tomitigate such an oblique camera view, a shift lens configuration may beemployed or the camera can be embedded with the projector in such a waythat they share the same optical path.

Once configured, the camera-projection component 110 can project imagesonto a display surface 120. The images can be rectified by way of animage processor component 130 and then displayed as a display image. Therectification process can involve performing calculations on an inputimage. Any calculations made on the image by the image processorcomponent can be related directly to the displayed image. That is, atracked position in the rectified image can be readily mapped to thecorresponding position in the displayed image. For example,rectification can be employed to remove any undesirable distortion fromthe input image. In practice, the camera-projection system can utilize awide angle lens which can impart significant barrel distortion on theinput image; while the oblique position of the camera imparts aprojective distortion or foreshortening. The image processor component130 can remove both distortions via standard bilinear interpolationtechniques. Parameters necessary to correct for lens distortion can berecovered by an off-line procedure.

The projective transform is determined by finding each of the fourcorners of the projected display by placing infrared reflective markers(paper) on the surface at known locations indicated by the projectedimage. Image rectification is illustrated in FIG. 4, infra. Note thatdue to the configuration of the system 100 and the assumption that theunit sits on the projection plane, this calibration step need not beperformed again when the unit is moved.

Any objects placed on or hovering over the display surface can bedetected, recognized, and/or tracked using the image processor component130. In particular, the image processor component 130 can detect objectstouching the surface without relying on special instrumentation of,underlying, or on the surface. Thus, the system 100 can operate on anyflat surface. More detailed information regarding the image processorcomponent 130 can be found in the discussion for FIGS. 4-11, infra.

Turning now to FIG. 3, there is a block diagram that comparesconventional projection systems with the subject projection-visionsystem (FIGS. 1 and 2). Most conventional projection-vision systemseither employ front projection with projector and camera mounted above(310) or rear projection with projector and camera in a cabinet (320).Unfortunately, there are disadvantages with both of these arrangements.

The top-down approach in 310 is rather popular since such mountingconsiderations are often necessary due to the throw requirements ofprojectors and the typical focal length of video cameras. However,ceiling installation of a heavy projector can be more than challenging,dangerous, can require special mounting hardware not easily accessibleby most consumers, and for all practical purposes may be best left toprofessional installers, which involves additional costs and lessaccessibility to the general public. Once installed, this top-downsystem and projection surface cannot be readily moved without requiringtedious or time-consuming re-calibration of the system. In addition,minor vibrations present in many buildings can create problems duringoperation and can make it difficult to maintain calibration. There isalso a possibility of occlusion of the projected image by a user's headand/or hands as they interact with the top-down system.

A second common approach is the rear projection set-up (320) wherein theprojector and camera are placed behind a diffuse projection screen.While this enables the construction of a self-contained device,eliminates some occlusion problems, and permits the placement of visualcodes on the bottom of objects, it is challenging at best to constructsuch a configuration with a large display area that also provides userswith sufficient room to put their legs under the table surface so thatthey may sit comfortably at the table. Furthermore, a dedicated surfaceis required and the resulting housing for the projector and camera canbe quite large and thus cumbersome and inconvenient for “anywhere”consumer use. It also presents significant manufacturing and productionproblems which may hinder yielding a marketable product.

Contrary to these common approaches, the subject configuration 330employs a camera and projector sitting off to the side of the active(projection) surface which mitigates many if not all of the drawbacksassociated with typical projection-vision systems. In fact, theapplication of this projector has a number of advantages. First, itavoids the often difficult and dangerous overhead installation of theprojector. Second, it is reasonable to assume that the plane of thesurface holding the projector is the projection plane. If the camera andilluminant are rigidly mounted to the projector as shown in FIG. 2,there is no need to re-calibrate the camera and projection to thesurface when the unit is moved. Similarly, since the height of thecamera and projector above the surface is constant, there are noproblems related to adjusting focal length of either the camera orprojector when the unit is moved.

Furthermore, with the oblique projection, occlusion problems typical ofconventional front-projected systems are minimized. For example, it ispossible for the user to stand over the system without their headoccluding the projected image. Finally, a 40″ diagonal projectionsurface which can be offered by the system is adequate for many advancedinteractive table applications, including complex gaming scenarios thatgo beyond simple board games and manipulation of multiple photos,printed pages, etc.

As previously mentioned, FIG. 4 demonstrates image rectification. Inparticular, initial image processing can remove lens distortion effectsfrom the input image 410 and matches the image to the display. Thecorresponding rectified image 420 is registered with the displayedimage. With image rectification, the input image 410 and projected imageare brought into one to one correspondence (e.g., a rectangular objecton the surface appears as a rectangular object in the image at the same(scaled) coordinates). One limitation of this process is that, due tothe oblique view of the camera, objects further away from the unit mayappear at a lower resolution. Consequently, the minimum effectiveresolution on the surface may be less than that of the acquired image(640×480 pixels).

Turning now to FIG. 5, there is a block diagram of a projection-visionsystem 500 that can sense visual coded objects on any interactiveprojection surface. The system 500 can include an object sensingcomponent 510 which can detect that a visual coded image is present onthe projection surface 520 or has moved to a new position on thatsurface 520. Once detected, the coded image can be captured by thecamera-projection component 110 and then subsequently projected back onthe projection surface 520 as a virtual object or onto other remotelyconnected display surfaces 530.

Visual codes have been applied in various augmented reality and tablescenarios, where they can be used to identify potentially any objectlarge enough to bear the code without recourse to complex generalizedobject recognition techniques. In tabletop, floor, or even wallscenarios, for instance, such visual codes are especially useful tolocate and identify game pieces, printed pages, media containers, knobs,and other objects that are generic in appearance but may vary inapplication semantics. As a knob, for example, an identified piece couldadjust the color and contrast of a digital photo. A number of visualcode schemes are used in augmented reality research. Here, a code formatand algorithm designed for the systems discussed herein is outlined.This code is particularly fast and can be implemented on GPU hardwarecurrently available and requires no search to determine codeorientation. Generally the problem of designing a code format is one ofbalancing the opposing goals of obtaining a simple detection algorithmthat works with the various transformations observed (e.g., translation,rotation) while supporting a useful number of code bits.

In the case of calibrated tabletop (or any other surface) visionsystems, including the subject system, where we may be interested ingame pieces on the surface, for example, the system can assume that eachinstance of the code appears in the image with known, fixed dimensions,thus simplifying the recognition and decoding process. The design of thesubject code, illustrated in FIG. 6, was driven from two observations.First, the presence and orientation of strong edges in the image may becomputed using uncomplicated, fast image processing techniques such asthe Sobel filter. Thus, if the code has a distinct edge as part of thedesign, the orientation of that edge can determine the orientation ofthe instance of the code. Secondly, if the code design supportssignificantly more bits than is needed for the application (e.g., anapplication may require only 12 unique code values, one for each of thegame piece types in chess, but the 12 bit code supports 4,096 uniquecodes values), then the code values may be chosen such that if one isfound through any process, the system is willing to take it as anindication of a valid instance of the code. These two observations usedtogether make for a practical detection algorithm, as follows:

-   -   1. Compute the edge intensity and orientation everywhere in the        image using the Sobel filter.    -   2. For each pixel with sufficiently high edge intensity, use the        edge orientation to establish a rotated local co-ordinate        system.        -   a. In the rotated coordinate system, read each pixel value            in the rectified image corresponding to each bit in the code            according to the code layout. Threshold each based on the            minimum and maximum value read, to arrive at a code value.        -   b. Check the code value against a table of codes used in the            current application. There is a candidate instance if a            match is found.    -   3. Rank each candidate according to some criteria (e.g.,        difference between maximum and minimum pixel values read).        Iterate until no more candidates: Take top ranked candidate as        valid code instance, and eliminate remaining candidates that        overlap.

In practice, depending on the code bit depth, the number of applicationcode values required and the nature of potential distracters in theimage, it may be necessary to add a further step that verifies theinstance. For example, consideration of image locations can be limitedto those that appear to be the center of circular contours of the gamepiece diameter. Such contours can be found quickly using the Houghtransform applied to circles, reusing the edge orientation informationcomputed above: a 2D histogram (image) representing the presence ofcircles centered at a given point is created by, for each pixel in theinput image, calculating the center of the circle of a given radius andedge orientation found at the input coordinates, and incrementing thehistogram at the calculated center. Each point in the resultinghistogram indicates the likelihood of a circle of the given radiuscentered there. FIG. 6 illustrates an exemplary visual code. Inparticular, a 3D graphics model is projected onto an identified gamepiece 610 with orientation determined by strong edge in the center ofthe pattern, and 12 bit code given by the pattern around the edge 620.One limitation of this scheme is that the user's hand can occlude avisual code. Without hysteresis or integration with the shadow-basedtouch algorithm, the system will conclude that the piece hasdisappeared. Shadow analysis as discussed in FIGS. 8-11 can be added tothe visual code decoding to resolve this.

The object sensing component 510 can also include an object trackingcomponent 540 that can track the movement of objects in real-time on theprojection surface 520. In particular, real objects can be captured andwhen detected, can cause their corresponding virtual objects to beprojected on the surface 520 for further manipulation or modification.For example, consider making a real charcoal drawing on paper. Thisdrawing could then be captured to an image precisely using the pagetracking information, and then later projected back onto the surface asa virtual object, or even onto a blank piece of paper, or another workin progress.

For instance, with regard to page tracking, the object trackingcomponent 540 can employ a page tracking algorithm that is based on aHough transform with the Sobel edge and orientation information asinput. This gives a histogram over orientation and perpendiculardistance to the origin which indicates the presence of strong lines inthe image. Given the dimensions of a page size to detect, it isstraightforward to find appropriate pairs of parallel lines a setdistance apart. Two pair of parallel lines perpendicular to each otheris verified as a page by ensuring that there are strong edges along asignificant fraction of the lines in the original Sobel image. Thisproportion can be tuned to allow for pages to overlap (e.g., FIG. 7).With this algorithm, multiple paper pages of known dimensions may becontinuously tracked by the system 500 with enough precision to projecta virtual image on the page as it is moved around the surface.Presently, multiple pages are tracked and disambiguated purely byassuming small frame to frame movement—not page appearance. Thistracking process also allows for pages to be turned 180 degreesrecognizably. Multiple (known) page sizes may also be simultaneouslydetected with minimal additional computation.

FIG. 7 shows page detection results and its application to theprojection of video onto physical pages. In particular, the figuredemonstrates a blank sheet 710 overlapping a printed sheet 720 and twodifferent images are then projected onto each sheet 730, 740. Inpractice, imagine that a different movie is projected onto each sheet.As a user moves around the surface (or table), each page can be movedaround the surface according to where the user is standing or sittingfor optimal viewing. It should be appreciated that the same image can beprojected onto each page such as when there are multiple users aroundthe table. Furthermore, any projected data can be communicated to aseparate or remote display surface. For example, imagine that a user isgiving a presentation using the main table or projection surface. One ormore other users sitting in the same room or in a different room canalso view the projected content in real-time.

Turning now to FIG. 8, there is a block diagram of a projection-visionsystem 800 that can determine whether objects are hovering or touchingthe surface by way of shadow analysis. FIGS. 9 and 10 provide a visualdemonstration. The system 800, and in particular a shadow analysiscomponent 810, can detect whether an object is touching the surface byexamining a change in appearance of shadows as an object approaches thesurface. FIG. 9 shows the (rectified) input image with two hands in thescene. The hand on the left is a few inches above the surface, while theindex finger of the hand on the right is touching the table surface.Note that as the index finger approaches the surface, the image of thefinger and its shadow come together, with the finger ultimatelyobscuring the shadow entirely at the point where it is on the surface.Because the illuminant is fixed with respect to the camera and surface,it should be possible to calculate the exact height of the finger overthe surface if the finger and its shadow are matched to each other andtracked. This height could be used as a hover signal for cursor controlor 3D cursor control.

Finger tracking may be performed however it would require making someassumptions about the appearance of the surface and fingers (e.g., thatfingers and the surface have significantly different brightness). Withshadow analysis, recovering the shadow reliably requires only that thesurface reflect infrared and that the device's infrared illuminant issignificantly brighter than stray infrared in the environment. Bothassumptions are reasonable given that the user is likely to place thedevice on a surface where the projection has good contrast andbrightness (e.g., not on a black surface or in a very bright room). Ashadow image can be computed from the rectified input by a simplethresholding operation (see FIG. 9). Candidate finger positions aregenerated by finding the highest (closest to the device) point on eachof the distinct shadows in the image which enter the scene from thebottom of the image (away from the device). These conditions typicallyyield a candidate for the most forward finger of each hand on thesurface, if the user is reaching in from the front, and rejects otherobjects on the surface that may generate their own shadows. Such fingercandidates may be found quickly by computing the connected components ofthe smoothed shadow image. Whether the finger is touching the surfacemay be determined by analysis of the shape of the shadow. FIG. 10 showsthe shadow at a finger tip for a finger on and off the surface. Thetracking component 810 can threshold the width of the finger shadowcomputed at a location slightly below the topmost point. In addition,this detection algorithm can be augmented by a verification algorithm,however, the provision that the candidate finger must lie on a shadowthat extends to the bottom of the image can tend to limit falsepositives if there are few other physical objects on the surface.Objects that are on the surface can be considered part of the shadow ifthey are particularly dark and can corrupt touch detection if they arenearby. Pointy dark objects are likely to generate false positives onlyif they extend to the bottom of the image and thus mimic arm shadows.

The images in FIGS. 9 and 10 demonstrate recovery of one finger per handbut it should be appreciated that one or more fingers per hand could bedetected in the manner described herein. More sophisticated finger shapeanalysis can be used to recover multiple fingers per hand perhaps atsome cost in robustness. Because very few assumptions about the shape ofthe hand are made, the pose of hand is not critical, and so the hand canbe relaxed. The precision of touch location is limited by the resolutionof the imaged surface, which has been subjectively estimated withgrating charts to be about 3-4 mm (approximately 4.5 image pixels).Simple trigonometry can be used to show that this spatial resolutionimplies a roughly equal resolution in the determination of height andtherefore touch accuracy by the method described above. This agrees withthe subjective experience of using the system.

FIG. 11 depicts exemplary applications of a finger detection scheme anda touch-based drawing application. In particular, the finger detectionscheme can be employed to open a button control panel or window such aswhen a finger is determined to hover or touch a designated area of thesurface. For example, a hovering finger can trigger the button panel toappear and a finger touch can press the button. It should be understoodthat the finger detection scheme (to determine touch or hover withrespect to any surface) can be integrated in a variety of computingdevices such as laptops, tablet PCs, PDAs, and mobile phonetechnologies.

Various methodologies will now be described via a series of acts. It isto be understood and appreciated that the subject system and/ormethodology is not limited by the order of acts, as some acts may, inaccordance with the subject application, occur in different ordersand/or concurrently with other acts from that shown and describedherein. For example, those skilled in the art will understand andappreciate that a methodology could alternatively be represented as aseries of interrelated states or events, such as in a state diagram.Moreover, not all illustrated acts may be required to implement amethodology in accordance with the subject application.

Referring to FIG. 12, there is a flow diagram illustrating an exemplarymethodology 1200 that facilitates determining whether an object istouching or hovering over the interactive surface in connection with aprojection-vision system. The method 1200 involves observing fingershadow(s) as they appear on an interactive (or projection) surface at1210. At 1220, one or more shadow images can be computed and based onthose images, the method can determine whether the one or more fingersare touching or hovering over the surface at 1230. When either a hoveror touch operation is determined, an appropriate action can follow. Forexample, if the hover is detected over a particular area of theinteractive surface, it can trigger a menu to appear on the surface. Auser can select menu options by using touch (e.g., touching the optionto select it). Alternatively, hovering can prompt a selection to be madeor can prompt some other pre-set operation to occur. Similar programmingcan be done with respect to a detected touch on the surface.

Turning now to FIG. 13, there is a flow diagram illustrating anexemplary methodology 1300 that facilitates page tracking. The method1300 involves detecting the presence of at least one page at 1310. Thiscan be accomplished in part by the presence of strong pairs (two) ofparallel edge lines that are perpendicular to each other. Page overlapcan also be accounted for and detected. At 1320, the page and/or itscontent, if any, can be captured as an image. At 1330, the image can beprojected (as a virtual representation of the real page) such as ontothe projection surface, onto another real or virtual page, or ontoanother work in progress.

Moreover, the projection-vision system as described herein offers acompact and readily portable unit that can be moved during use withoutrequiring re-calibration of the system. The system can be employed forwork, play, entertainment, or any other purpose. The exemplaryconfigurations of the system are included merely for demonstration ofthe various components arranged in a single unit but are not meant tolimit the system to a particular size, dimension, or configuration.Processors and memory storage can also be included in the configuration.When put into use, the projection-vision system can project virtualrepresentations of items or objects and permit manipulation or otherinteraction of them by one or more users. Thus, the projection surfacebecomes an interactive surface, allowing users to perform variouscomputing operations, content modification, and navigation of theprojected content such as panning, zooming, and scrolling. Inparticular, flow field technology can be employed or integrated with theprojection-vision system to facilitate such navigational techniques whenviewing projected images (e.g., map, architectural plans, etc.)

In order to provide additional context for various aspects of thesubject invention, FIG. 14 and the following discussion are intended toprovide a brief, general description of a suitable operating environment1410 in which various aspects of the subject invention may beimplemented. While the invention is described in the general context ofcomputer-executable instructions, such as program modules, executed byone or more computers or other devices, those skilled in the art willrecognize that the invention can also be implemented in combination withother program modules and/or as a combination of hardware and software.

Generally, however, program modules include routines, programs, objects,components, data structures, etc. that perform particular tasks orimplement particular data types. The operating environment 1410 is onlyone example of a suitable operating environment and is not intended tosuggest any limitation as to the scope of use or functionality of theinvention. Other well known computer systems, environments, and/orconfigurations that may be suitable for use with the invention includebut are not limited to, personal computers, hand-held or laptop devices,multiprocessor systems, microprocessor-based systems, programmableconsumer electronics, network PCs, minicomputers, mainframe computers,distributed computing environments that include the above systems ordevices, and the like.

With reference to FIG. 14, an exemplary environment 1410 forimplementing various aspects of the invention includes a computer 1412.The computer 1412 includes a processing unit 1414, a system memory 1416,and a system bus 1418. The system bus 1418 couples system componentsincluding, but not limited to, the system memory 1416 to the processingunit 1414. The processing unit 1414 can be any of various availableprocessors. Dual microprocessors and other multiprocessor architecturesalso can be employed as the processing unit 1414.

The system bus 1418 can be any of several types of bus structure(s)including the memory bus or memory controller, a peripheral bus orexternal bus, and/or a local bus using any variety of available busarchitectures including, but not limited to, 11-bit bus, IndustrialStandard Architecture (ISA), Micro-Channel Architecture (MCA), ExtendedISA (EISA), Intelligent Drive Electronics (IDE), VESA Local Bus (VLB),Peripheral Component Interconnect (PCI), Universal Serial Bus (USB),Advanced Graphics Port (AGP), Personal Computer Memory CardInternational Association bus (PCMCIA), and Small Computer SystemsInterface (SCSI).

The system memory 1416 includes volatile memory 1420 and nonvolatilememory 1422. The basic input/output system (BIOS), containing the basicroutines to transfer information between elements within the computer1412, such as during start-up, is stored in nonvolatile memory 1422. Byway of illustration, and not limitation, nonvolatile memory 1422 caninclude read only memory (ROM), programmable ROM (PROM), electricallyprogrammable ROM (EPROM), electrically erasable ROM (EEPROM), or flashmemory. Volatile memory 1420 includes random access memory (RAM), whichacts as external cache memory. By way of illustration and notlimitation, RAM is available in many forms such as synchronous RAM(SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rateSDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), anddirect Rambus RAM (DRRAM).

Computer 1412 also includes removable/nonremovable, volatile/nonvolatilecomputer storage media. FIG. 14 illustrates, for example a disk storage1424. Disk storage 1424 includes, but is not limited to, devices like amagnetic disk drive, floppy disk drive, tape drive, Jaz drive, Zipdrive, LS-100 drive, flash memory card, or memory stick. In addition,disk storage 1424 can include storage media separately or in combinationwith other storage media including, but not limited to, an optical diskdrive such as a compact disk ROM device (CD-ROM), CD recordable drive(CD-R Drive), CD rewritable drive (CD-RW Drive) or a digital versatiledisk ROM drive (DVD-ROM). To facilitate connection of the disk storagedevices 1424 to the system bus 1418, a removable or non-removableinterface is typically used such as interface 1426.

It is to be appreciated that FIG. 14 describes software that acts as anintermediary between users and the basic computer resources described insuitable operating environment 1410. Such software includes an operatingsystem 1428. Operating system 1428, which can be stored on disk storage1424, acts to control and allocate resources of the computer system1412. System applications 1430 take advantage of the management ofresources by operating system 1428 through program modules 1432 andprogram data 1434 stored either in system memory 1416 or on disk storage1424. It is to be appreciated that the subject invention can beimplemented with various operating systems or combinations of operatingsystems.

A user enters commands or information into the computer 1412 throughinput device(s) 1436. Input devices 1436 include, but are not limitedto, a pointing device such as a mouse, trackball, stylus, touch pad,keyboard, microphone, joystick, game pad, satellite dish, scanner, TVtuner card, digital camera, digital video camera, web camera, and thelike. These and other input devices connect to the processing unit 1414through the system bus 1418 via interface port(s) 1438. Interfaceport(s) 1438 include, for example, a serial port, a parallel port, agame port, and a universal serial bus (USB). Output device(s) 1440 usesome of the same type of ports as input device(s) 1436. Thus, forexample, a USB port may be used to provide input to computer 1412, andto output information from computer 1412 to an output device 1440.Output adapter 1442 is provided to illustrate that there are some outputdevices 1440 like monitors, speakers, and printers among other outputdevices 1440 that require special adapters. The output adapters 1442include, by way of illustration and not limitation, video and soundcards that provide a means of connection between the output device 1440and the system bus 1418. It should be noted that other devices and/orsystems of devices provide both input and output capabilities such asremote computer(s) 1444.

Computer 1412 can operate in a networked environment using logicalconnections to one or more remote computers, such as remote computer(s)1444. The remote computer(s) 1444 can be a personal computer, a server,a router, a network PC, a workstation, a microprocessor based appliance,a peer device or other common network node and the like, and typicallyincludes many or all of the elements described relative to computer1412. For purposes of brevity, only a memory storage device 1446 isillustrated with remote computer(s) 1444. Remote computer(s) 1444 islogically connected to computer 1412 through a network interface 1448and then physically connected via communication connection 1450. Networkinterface 1448 encompasses communication networks such as local-areanetworks (LAN) and wide-area networks (WAN). LAN technologies includeFiber Distributed Data Interface (FDDI), Copper Distributed DataInterface (CDDI), Ethernet/IEEE 1102.3, Token Ring/IEEE 1102.5 and thelike. WAN technologies include, but are not limited to, point-to-pointlinks, circuit switching networks like Integrated Services DigitalNetworks (ISDN) and variations thereon, packet switching networks, andDigital Subscriber Lines (DSL).

Communication connection(s) 1450 refers to the hardware/softwareemployed to connect the network interface 1448 to the bus 1418. Whilecommunication connection 1450 is shown for illustrative clarity insidecomputer 1412, it can also be external to computer 1412. Thehardware/software necessary for connection to the network interface 1448includes, for exemplary purposes only, internal and externaltechnologies such as, modems including regular telephone grade modems,cable modems and DSL modems, ISDN adapters, and Ethernet cards.

What has been described above includes examples of the subject systemand/or method. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the subject system and/or method, but one of ordinary skillin the art may recognize that many further combinations and permutationsof the subject system and/or method are possible. Accordingly, thesubject system and/or method are intended to embrace all suchalterations, modifications, and variations that fall within the spiritand scope of the appended claims. Furthermore, to the extent that theterm “includes” is used in either the detailed description or theclaims, such term is intended to be inclusive in a manner similar to theterm “comprising” as “comprising” is interpreted when employed as atransitional word in a claim.

1. A system comprising: a memory; a processing unit coupled to thememory; an object sensing component executed by the processing unit andconfigured to sense an object over an interactive surface, theinteractive surface being illuminated with an infrared source; a shadowanalysis component executed by the processing unit and configured to:track a shadow of the object appearing on the interactive surface basedon the interactive surface reflecting infrared when the object ismoving; and enable touch detection by examining the shadow of the objectto determine if the object is hovering over or touching the interactivesurface based on an analysis of the shadow of the object.
 2. The systemof claim 1, wherein the object sensing component is further configuredto trigger content to appear on the interactive surface based on theobject being determined as hovering or touching the interactive surface.3. The system of claim 1, wherein the object sensing component isfurther configured to trigger content to appear on the interactivesurface to enable the object to interact with the content on theinteractive surface via touching the interactive surface.
 4. The systemof claim 1, wherein the object sensing component is further configuredto trigger a menu including menu options to appear on the interactivesurface based on the object being determined as hovering, the menuoptions selectable by the object via touching the interactive surface.5. The system of claim 1, the system configured to be integrated into alaptop, a tablet computer, a personal digital assistant, or a cellulartelephone.
 6. A method implemented at least partially by a processor,the method comprising: illuminating an interactive surface; detecting anobject over the interactive surface being illuminated with the infraredsource; observing a shadow of the object appearing on the interactivesurface based on the object being detected; reflecting infrared by theinteractive surface based on the shadow of the object; and determiningthat the object the object is hovering or touching the interactivesurface based on an analysis of the shadow of the object.
 7. The methodof claim 6, wherein the determining the object is touching theinteractive surface based at least in part on a binarized image of theobject and the shadow of the object.
 8. The method of claim 6, furthercomprising determining that the finger is not touching the interactivesurface based at least in part on the finger and the shadow of thefinger yielding two images.
 9. The method of claim 6, further comprisingcalculating a height of the object over the interactive surface when theobject and the shadow of the object are matched to yield one image,wherein the height serves as a signal for cursor control.
 10. The methodof claim 6, wherein when the finger is detected triggering a buttonpanel or a window to appear.
 11. The method of claim 10, furthercomprising enabling a touch to press the button panel or the window inthe interactive surface.
 12. One or more computer-readable media storingcomputer-executable instructions that, when executed by one or moreprocessors, cause the one or more processors to perform acts comprising:illuminating at least a portion of a physical surface; observing ashadow of a object appearing on the portion of the physical surfacebeing illuminated; and determining the object is hovering over ortouching the portion of the physical surface based on an analysis of theshadow of the object.
 13. The one or more computer-readable media ofclaim 12, wherein the illumination is infrared illumination.
 14. The oneor more computer-readable media of claim 12, the acts further comprisingdetecting an object over the portion of the physical surface beingilluminated.
 15. The one or more computer-readable media of claim 14,the acts further comprising calculating a height of the finger over thephysical surface when the object and the shadow of the object arematched to yield one image, wherein the height serves as a signal forcursor control.
 16. The one or more computer-readable media of claim 14,the acts further comprising determining that the object is not touchingthe portion of the physical surface based at least in part on the objectand the shadow of the object yielding two images when the finger and theshadow of the object are binarized.
 17. The one or morecomputer-readable media of claim 14, the acts further comprisingdetermining that the object is touching the portion of the physicalsurface based at least in part on binarizing the object and the shadowof the object to yield one image.
 18. The one or more computer-readablemedia of claim 12, the acts further comprising: determining that theobject is hovering over the portion of the physical surface; andtriggering a button panel or a window to appear.
 19. The one or morecomputer-readable media of claim 18, the acts further comprisingenabling a touch to press the button panel or the window.
 20. The one ormore computer-readable media of claim 12, the acts further comprisingtriggering content to appear on the portion of the physical surface inresponse to determining that the object is hovering over or touching theportion of the physical surface.